Brake mechanism



July 29, 1930. y Q L SMH-H 1,771,969

BRAKE MECHANISM v Filed Dec. 5, 1928 3mm/nier 54 Geofgelldmw Patented July 29, 193o` UNITED STATES PATENT osi-ica f GEORGE L. SMITH, F WASHINGTON, DISTRICT OF COLUMBIA.,- ABSIGNOR T0 UNITED STATES OIRDNAlI'ZEV COMPANY, OF WASHINGTON, DISTRICT OF COLUMBIA, A OOR- POBATION OF VIRGINIA l ,BRAKE MECHANISH .Application mea December '5, 192s. senim. 323,922.

' As is well-known, a'brake of the so-called full wrap type, that is, a brake which extends substantially 360 with respect to arelated drum and has its anchor located at one end thereof, as distinguished from a/ brake of the so-called half wrap or other type, in which the anchor is located intermediate the ends of the brake, develops maximum braking power for a given pressure exerted to apply it. At 113 the same time it also is Well known that a brake of the full wrap type, especially an internal brake of this type, is inclined to be very erratic in its action due to the fact that slight variations in thecoeilicient of friction between the brake lining and a related drum produce extensive changes in the power of thel/ brake. Accordingly it is the purpose of my present invention to provide means to equalize the braking eects of a pair of full'- wrap brakes, that is., to rovide means to reduce thel pressure on t e brake where the brake power is high and. to correspondingly increase the pressure on the brake where brake power .isflow, whereby uctuations in the combined power of the brakes for any .given brake a plying pressure are reduced to a marked egree and whereby the braking edect of each brake is maintained substantially the same as the other. It also is my purpose to provide a brake actuating mechanism which will apply a.

brake actuating'force in a .direction to reduce to a minimum the liability of the brakes grabbing or locking when applied.

In my prior Patent 1,490,642, issued April 15, 1921i, the brake bands are permitted a limited amount of free mtation to move the compensating links ed of their dead centers. ln my present invention I avoid this free rotation and conse uently reduce to a minimum the movement ot the brake actuatin mechanism necessary to apply the brakes y placing the bell-crank arms between the ends of the brakes, so that when the b1 aires are enpanded, clearances are provided lfor v the swinging movement el the bellneranks.

ln my aforesaid prior patent the equalizf ing ll-cranks are swun with respect tothe steering wheels when t e latter are moved angularly to edect ring, the result being that although the brakes ma be equal in braking power for straight a ead travel of the vehicle, angularsteering movements of the-wheels will tend tov further apply the brakes. Accordingly it is another purpose of my present invention so to arrange the equali'zing bell-cranks as to eliminate an swinging movement of s'aid bell-cranks wit respect to their related wheels due to the latter being swung angularly to effect steering.

The equalizing'cross rod employed to connectthe equalizing bell-cranks of my invenvention at times operates in tension and at other times in' compression and it is another of in! present purposes to provide means to avoi the danger of lsaid'rod becoming bent as a result of operating in compression.

With the foregoing and other purposes in view, m invention consists in the novel'jfeatures o construction, combination and arrangement of parts as will be hereinafterA .more fully described, illustrated in the accom anying drawings and defined-in the appen ed claims. l

In the drawings, wherein like .characters of reference denote corresponding parts in 'the different views- Fi. l is a side elevation partly in section of a rake embodying the novel features'. ci mfy present invention, the illustration being o a right front brake as viewed from a point to the right thereof;

Fig. 2, a section on the line'2-72 of Fig. 1;

Fig. 3,l a diagrammatic view illustratingvv designates a brake drum mounted in theV usual manner on a wheel, not shown, while il desites a backing plate bolted or other wise secured as at l2 to a steerinly l-rnuckle 13. The brake, which is-ot the full wrap ty e, .is composed in this instance ottwo dexile shoes lll and l5 joined together .at their upper ends by an suiteble adjusting device A and formed at t eirv lower ende to reet i Mill opposite sides of the short arm 16 ot an equalizing bell-crank C, the end 17 of one of the shoes, shoe it in this instance, being straight to match the straight face 18 of the arm 16 of the bell-crank, and the end19 of the other shoe, shoe in this instance, being curved to match the curved or pivoting face 20 of the arm i6 of the bell-crank, which curved or' pivoting face is opposite the tace i8. These exihle shoes partake of the nature ot an expanding brake hand at the portions ld, hut are of increasing stiness approaching their lovver ends due to side anges oli4 increasing depth. rthey can therefore he called reinforced bands as Well as exible shoes, and more correctly so, as shoes usually require pivotal connections to the hacking plate 1l, 'Whereas the loralres shown do not require such connections.

rEhe hellcranlr is pivoted as at 21 to a braclret 22 vvhich is secured to the backing plate 1l, the pivot 2 being located abreast the usual lring pin 23and at such a distance avvaytrom it that the long arm 2t of the bell-crank may rbe' laid parallel or in other suitable spaced relation to the hacking plate 'il so vas to permit said arm to swing, said arm terminating in a pivot 25 which is located, when the ivheel with which the brake is associated is straight aheadposition, on'a'line fui-) passing through the center oi the hing pin 23 and tie pivot 26 at 'the outer end et the usual steering arm 2T. particularly to Fig. 3 ofivthe drawings which illustrates a pair et steering "wheel lorales operatively connected with one another, i tvill he observed that the pivots at the outer ends of the hell-crank arms are connected together loy an equalizing cross rod 28 and the pivots 26 at the-outer ends oil steering arms 27 are connected together hy a steering tie rod 29, Aliso, it will he ,observed that vvith the steering Wheels lil positioned iter straight ahead travel, the lines o-- extended, intersect'at a point 'O short distance orvvaidly ci the rear axle hviously, therethro, the iength ci the steering arms 2'?, Whether seid arms extend forwardly or rearwardly with respect to the steering Wheels WJ, he varied Without steering movements ot the Wheels for any given angular movement oi an associated. steering Wheel, provided the piv-b1 loeated on the lines tif-"o, respec- 2@ are t tively, as atoresard, @bvtously, too, due to toe 'tertk the heitcranss 'C are mounted yon tht-)hacking plates il so as to string with the Wheels it "follows that so long as the pivote are located on the lines awo, no pivotinI noveinent the hell-cranks with respect to the Wheels will occur es a reu wheels moved singularly etlect lvlenicstlv, therefore, the v a e .e `length or the eelt-cranks may also loe v Without relation avviso@ of the parts of the brakes when the Wheels W are swung angularly topeilect steering, provided the pivots 25 are, as aforesaid, located on the lines a-b When the Wheels l are positioned for straight ahead travel. Thus it is apparent that with the brakes unapplied no brake applying movement vvill be imparted to the shoes 14, 15 due to the Wheels W being swung angularly to eiect steering, as would he the case it the parts of the mechanism Were so relatively arranged that pivotal movements of the bell-crank C s,

with respect to the Wheel W occurred When angular steering movements Were imparted to the Wheels.

For expanding the shoes 1li, 15 into braking engagement with the drums 10 l provide for each brake a toggle mechanism consisting oi' a thrust link 30 disposed horizontally above the arm 16 oit the bellcrank C and pivoted at oneend, as at 31, to one of the shoes 14 or l5, to shoe l5 in this instance, and at its other end, as at 32, to one arm of a bell-crank 33 which is pivoted, as at 34, to the other of said shoes,.a vertically extending pull rod 35 being pivoted at its lower end to the second arm et said bell-crank 33, as at 36, and at its upper end to a lever 37, which lever is pivoted over the head ot the hing pin23 and is adapted for connection in suitable or preferred manner with pedal, 'ever or other brake actuating device B as shown in Fig. 3 oit the drawings.

As illustrated in Fig. 1 oi the drawings, the relative arrangement oiq thrust link 30, hell-crank 33 and pull rod 35 is such that thrust on pivot 34 when the brake is applied,

is in a direction, indicated by line ce-al, parallel or substantially parallel to a tangent to the brake drum at a point near said pivot, which is, as experiments have shown, the most eective direction in producing braking pressure and substantially eliminates any tendency ot the brake to grab or loclr when applied. rlhis line c-CZ is ned as follows: rlhrirst on linlr 30 is in a line with pivots 31h-3Q. The pull on pivot 36 is in the direction of rod 35. The line eze-ol must therefore pass through pivot 3l and through the intersection oi' line B1-32' extended with airis of rod 35,.

positioning pivot 32 so that there vvill be hut f little swinging movement or link 30, it is seen that the direction oit line 0-d ivili he unchanged regardless ot weer of the braise lining.

As a result ot my improved structure as shovvn and described.. is apparent that with the hralres unapplied, the cooperation or the `laces 17 i8, i9 and 20 results in the equalizing bell-cranks heine' held in neutral positions from which they may swing in either direction produce equalization of the braking ettects, @n the other hand, when the altes are applied, ahead rotation. et the drums l@ tclocirwise viewed in Fig. l) will tend to impart corresponding rotation to the shoes 14, 15. Rotation of said shoes will, however, be arrested by Contact of the ends 19 of the shoes 15 with the curved faces 2() of the short arms 16 of the bell-crank C, so that gaps will open up between the opposite or fiat faces 18 of the bell-crank arms 16 and the adjacent ends 17 of the shoes 14, which gaps will permit such swinging movement of the bellcranks C as may be required to effect equaliza-l tion to take place without either end of the face 18 of either bell-crank coming into contact with the end 17 of the related shoe 14. Thus free movement'of the bell-cranks'C and of the cross rod 28 to effect equalization is permitted. On the .other hand, in the event of brake application to retard rearward ro` tation of the drums 10, the ends 17 of the shoes 14 will be pressed forcibly against the faces 18 of the bell-crank arms 16, and since said ends 17 and said faces 18 are straight, no equalizing action will occur, but to the contrary each bell-crank, because of the cooperation ofsaid straight faces 17--18, will hold its'related shoe 14 in the-same position at all times. The bell-cranks C and cross rod 28 operate to eiect equalization of the braking effects of the two brakes in the manner set forth in connection with the equalizing bell-cranks and cross rods shown in either of my prior Patents 1,440,842; 1,490,642 or 1,503,609.

As shown in Figs. 2 and 3, the equalizing cross rod 28 is positioned in advance of the steering tie rod 29 and is supported from the latter byvsteady-rests 38.. In some cases however, it may be desirable and advantageous to house the equalizing cross rod within a tubular steering tie rod as shown in Fig. 4 which may be accomplished by providing offset pivots 26 between the steering arms 27 and a tubular tie rod 29 and positioning the pivots 25 connecting the ends of the equalizing vbell-cranks and the cross rod 28 in vertical alinement with said pivots 26.

In the claims the term braking ei'ect is used to describe the actual retarding force which a braked wheel exerts on the ground. This may or may not correspond to the brake force as it is not only dependent upon this force, but also upon the adhesion or holding power of the tire on the ground. For instance, if this adhesion is low, the brake force may be suiicient to lock the wheel .and any further brake force applied would be ineffectual to increase this braking e'ect.

I claim:

1. In a brake system, the combination with a pair of vehicle steering wheels angularly movable about spaced axes to effect steering,

a brake for each wheel consisting of a Wheel carried drum and al cooperating brake ele wheel anda tie rod pivotally connected at its ends with said arms, respectively; of means anchoring said brake elements consisting of a pair ofbell-cranks corresponding arms of which are in operative engagement with said brake elements, respectively, and a cross rod the ends yof which are pivotally connected with the other arms` of said bell-cranks, respectively, the pivots between the ends of said cross rod and said bell-crank arms being located, when the wheels are positioned for straight ahead steering and when the brakes are unapplied, on lines passing through the steering axes of said wheels and the pivotal connections between said tie rod and said steering arms, respectively.

2. In a brake system, the combination with a pair of steering Wheels angularly movable about spaced axes to eii'ect steering, a brake for each wheel, and steering mechanism for said wheels includingra steering arm extending fromveach wheel and a tie rod connecting said arms, of means anchoring 1 `a pair of steering Wheels angularly movable about spaced axes to effect steering, a brake for each'wheel, and steering mechanism for said wheels including a steering arm extending from each wheel and a tie rod connecting -said arms; of means anchoring said brakes 'l against all similarly directed rotary movements consisting of' a pair of bell-cranks operatively connected with said brakes,respec tively, and connected together by a cross rod. one of said rods being hollow and the other being housed therein.

4. In a brake system of the band type, the combination with duplicate full -wrap brake bands and a common brake band operating device, of means between the bands cooperating with one end .of each of said bands and with said device through the bands to equalize the brakin effects of the latter.

5. Ina rake system including duplicate brakes anda common brake applying device, the combination of two full wra brake elements, inl which gaps are provi ed between the ends thereof, an anchoring mechanism extending between the. brakes and into said gaps movable in either direction from a neutral vposition and cooperating with said device to e'ect equalization of the braking e'ects of said brakes, and means whereby said brake elements hold said anchoring mechanism in nutal position when the brakes are imapp 1e 6. fIn a brake system, the combination with a pair of brakes of the full wrap type; of a common brake applying mechanism and wir brakes.

7. ln a brake system, the combination with a pair of brakes of theinternal expanding full wrap type; of a common brake expanding mechanism and anchoring -means engaging the endsot said brakes and cooperating with said mechanism to equalize the braking eects of said brakes.

8. ln a brake system, the combination with a pair of brakes of the internal full wrap type, in which gaps are provided between the ends of the brakes, respectively, of a common brake applying mechanism and brake anchoring means extending between the brakes and into said gaps for engaging the ends of the brakes and cooperating with said mechanism to equalize the braking eect of said brakes.

9. ln a brake system, the combination with a pair of brakes of the internal expanding full wrap band type, of a common brake eX- panding mechanism and anchoring means engaging the bands of said brakes between the ends thereof and cooperating with said mechanism to equalize the braking effects oit said brakes, said means being in Contact with both ends of the bands when the latter are contracted.

10. ln a brake system, the combination with a pair of brakes of the interna-l full wrap type; of means anchoring said brakes against all similarly directed rotary movements, said means consisting oit a pair of piybtally mounted bell cranks corresponding arms of which are disposed between the ends of said brakes respectively, and the other arms of which are connected by a cross rod.

ll. ln a brake system, the combination with a pair ot' brakes of the internal expanding full wrap type; oa common brake expanding mechanism and means anchoring said brakes consisting of a pair of pivotally mounted bell-cranks corresponding arms of which are disposed between and in contact with thev ends of said brakes, respectively, when the latter are contracted, and the other arms of which are connected together by a cross-rod, said means cooperating with said mechanism to equalize the-braking e'ects ot said brakes.

l2. ln a brake system, the combination with a pair of vehicle steering wheels anunlarly movable about spaced axes to epect steering, and a brake for each wheel'consisting ot a wheel carried drum and a cooperating brake element; of means anchorin said brake elements consisting of a pair o bellcranks, mounted on pivots substantially parallel to said spaced axes; corresponding arms of which bell-cranks are in operative engagement with said brake elements, respectively, and the other arms of which are pv'otally connected by a cross-rod, said pivotal connections mames signature. 70

GEORGE L. SMTH.' 

